Test: Science & Technology - 3 (August 20, 2021)


25 Questions MCQ Test UPSC CSE Prelims 2021 Mock Test Series | Test: Science & Technology - 3 (August 20, 2021)


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This mock test of Test: Science & Technology - 3 (August 20, 2021) for UPSC helps you for every UPSC entrance exam. This contains 25 Multiple Choice Questions for UPSC Test: Science & Technology - 3 (August 20, 2021) (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Science & Technology - 3 (August 20, 2021) quiz give you a good mix of easy questions and tough questions. UPSC students definitely take this Test: Science & Technology - 3 (August 20, 2021) exercise for a better result in the exam. You can find other Test: Science & Technology - 3 (August 20, 2021) extra questions, long questions & short questions for UPSC on EduRev as well by searching above.
QUESTION: 1

Which of the following is/are the necessary properties required by a molecule to act as genetic material?

1. It should be able to generate its replica.

2. It should be chemically and structurally stable.

3. It should be able to express itself in the form of "Mendelian Characters".

Select the correct answer using the code given below.

Solution: Any material of plant, animal, microbial or another origin that carries genetic information and that passes it from one generation to the next. The information contained controls reproduction, development, behavior, etc. Some of the essential features of genetic material are

The genetic material should be stable enough not to change with different stages of the life cycle, age or with a change in the physiology of the organism.

Since genetic material carries information from the parents to the offsprings, therefore, they should be able to replicate.

A genetic material should be chemically and structurally stable so as to maintain its integrity with age, cell cycle and different physiology of individuals.

They should also have the capability of slow changes so that evolution is supported.

'Mendel characters' means the characters which follow the inheritance pattern proposed by Mendel. Mendelian characters are basically the law of inheritance. They should be able to express themselves in the form of Mendelian characters. Genetic materials are transmitted from parents to off-springs and hence off-springs inherit dominant characteristics of their parents.

Hence all the three statements are correct.

QUESTION: 2

Which among the following hormones is/are produced by the human body?

1. Insulin

2. Cytokinin

3. Thyroxine

Select the correct answer using the code given below.

Solution: Insulin is a hormone made by the pancreas that allows the body to use sugar (glucose) from carbohydrates in the food or to store glucose for future use. Insulin helps keep blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia).

Cytokinins are a class of plant growth substances (phytohormones) that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence.

Thyroxin is the main hormone secreted into the bloodstream by the thyroid gland. It is the inactive form and most of it is converted to an active form called triiodothyronine by organs such as the liver and kidneys. Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones.

QUESTION: 3

Consider the following parts of the human eye:

1. Cornea

2. Retina

3. Lens

In the case of eye donation, which of the above parts is/are transplanted from the donor?

Solution: The cornea is the clear bulging surface in front of the eye. It is the main refractive surface of the eye.

The lens is the transparent body enclosed in an elastic capsule. It is made up of proteins and water.

The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The purpose of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. Whole eye transplants are still in the experimental stages, parts of the eye can be surgically replaced with donor tissue.

Corneal part of the donor's eye is transplanted in the eye donation process; the rest of the parts are not used. Hence only option 1 is correct.

QUESTION: 4

Isotopes have the same atomic number but different atomic masses. Which among the following are the uses of radioactive isotopes?

1. Treatment of cancer

2. Fuel in nuclear reactors

3. Treatment of goitre

Select the correct answer using the code given below.

Solution: A major characteristic of an atom is its atomic number, which is defined as the number of protons. The chemical properties of an atom are determined by its atomic number. The total number of nucleons (protons and neutrons) in an atom is the atomic mass number. Atoms with the same atomic number but with different atomic masses are called isotopes. Isotopes have identical chemical properties, yet have very different nuclear properties. For example, there are three isotopes of hydrogen. Two of these isotopes are stable (not radioactive), but tritium (one proton and two neutrons) is unstable. Most elements have stable isotopes.

Radioactive isotopes can also be created for many elements. An isotope of uranium (Uranium-235) is used as a fuel in nuclear reactors. An isotope of cobalt (Cobalt-60) is used in the treatment of cancer. An isotope of iodine (Iodine-131) is used in the treatment of goitre.

QUESTION: 5

Consider the following statements regarding the speed of sound in a different medium:

1. Among the three states solid, liquid and gaseous, sound travels fastest in the gaseous state.

2. Sound travel travels faster in hot air than in cold air.

Which of the statements given above is/are correct?

Solution: The closer the molecules are to each other and the tighter their bonds, the less time it takes for them to pass the sound to each other and the faster sound can travel. It is easier for sound waves to go through solids than through liquids because the molecules are closer together and more tightly bonded in solids. Thus, speed travels fastest in solids and slowest in gas. Hence statement 1 is not correct.

Heat, like sound, is a form of kinetic energy. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly. The speed of sound in room temperature air is 346 meters per second. This is faster than 331 meters per second, which is the speed of sound in air at freezing temperatures. Hence statement 2 is correct.

QUESTION: 6

Which among the following are the uses of heavy water?

1. Preservation of Oral Polio Vaccines

2. Coolant in nuclear reactors

3. Bleaching agent

Select the correct answer using the code given below.

Solution: A pressurized heavy-water reactor (PHWR) is a nuclear reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water (deuterium oxide D2O) as its coolant and neutron moderator.

Non-Nuclear Applications of heavy water include: Preservation of Oral Polio Vaccines, Deuterated drugs for enhancement of biological efficacy, Deuterated optical fibers to enhance transmission efficiency etc.

Heavy water is not used as a bleaching agent. Hydrogen peroxide is the simplest peroxide and is used as an oxidizer, bleaching agent and antiseptic.

QUESTION: 7

Which of the following treaties, under the auspices of the United Nations, have been ratified by India?

1. Convention on the Elimination of All Forms of Discrimination against Women.

2. Convention on the Rights of Persons with Disabilities.

3. Convention against Torture and Other Cruel Inhuman or Degrading Treatment or Punishment.

Select the correct answer using the code given below.

(d 1, 2 and 3

Solution: The Convention on the Elimination of All Forms of Discrimination against Women (CEDAW), adopted in 1979 by the UN General Assembly, is often described as an international bill of rights for women. By accepting the Convention, States commit themselves to undertake a series of measures to end discrimination against women in all forms. India signed the treaty in 1980 and ratified it in 1993.

The Convention on the Rights of Persons with Disabilities is an international human rights treaty of the United Nations intended to protect the rights and dignity of people with disabilities. Parties to the Convention are required to promote, protect, and ensure the full enjoyment of human rights by people with disabilities and ensure that they enjoy full equality under the law. India signed and ratified the treaty in 2007.

The Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (commonly known as the United Nations Convention against Torture (UNCAT)) is an international human rights treaty, under the review of the United Nations, that aims to prevent torture and other acts of cruel, inhuman, or degrading treatment or punishment around the world. India signed the treaty in 1997 but has not ratified it as yet.

QUESTION: 8

Edge computing is used for data processing and content delivery. What are the advantages of Edge computing over Cloud computing?

1. Edge computing allows quicker data processing

2. In Edge computing, data is stored and processed in the centralised data center

3. Internet of Things (IoT) based technology could be using Edge computing for analytics.

Select the correct answer using the code given below.

Solution: The word edge in this context means literal geographic distribution. Edge computing is computing that’s done at or near the source of the data, instead of relying on the cloud at one of a dozen data centers to do all the work. It doesn’t mean the cloud will disappear. It means the cloud is coming to you.

Edge computing enables data to be analyzed, processed and transferred at the edge of a network. The basic difference between edge computing and cloud computing lies in where the data processing takes place. In Edge computing, The idea is to analyze data locally, closer to where it is stored, in real-time without latency, rather than send it far away to a centralized data centre. Hence statement 2 is not correct.

So whether you are streaming a video on Netflix or accessing a library of video games in the cloud, edge computing allows for quicker data processing and content delivery. Hence statement 1 is correct.

At the moment, the existing Internet of Things (IoT) systems perform all of their computations in the cloud using data centers. Edge computing, on the other hand, essentially manages the massive amounts of data generated by IoT devices by storing and processing data locally. That data doesn’t need to be sent over a network as soon as it is processed; only important data is sent — therefore, an edge computing network reduces the amount of data that travels over the network. Hence statement 3 is correct.

QUESTION: 9

Consider the following statements regarding virtual reality (VR) and augmented reality (AR):

1. The real and virtual objects cannot be distinguished in VR whereas they can be distinguished in AR.

2. Both VR and AR can be viewed by users wearing special glasses only.

Which of the statements given above is/are correct?

Solution: Augmented Reality blends virtual reality and real life, but users continue to be in touch with the real world while interacting with virtual objects around them, so they can distinguish between the two.

Virtual Reality creates an entirely fabricated world, that users would find it difficult to tell the difference between what is real and what is not. Hence, statement 1 is correct.

VR is usually possible by wearing a VR helmet or goggles while AR does not require users to wear special glasses. Hence, statement 2 is not correct.

QUESTION: 10

Consider the following statements regarding 'Halogens':

1. They are non-metallic elements that produce sodium salts of similar properties.

2. Because of their great reactivity, the free halogen elements are not found in nature.

Which of the statements given above is/are correct?

Solution: Halogen element, any of the six nonmetallic elements that constitute Group 17 (Group VIIa) of the periodic table. The halogen elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). They were given the name halogen, from the Greek roots hal- (“salt”) and -gen (“to produce”), because they all produce sodium salts of similar properties, of which sodium chloride—table salt, or halite—is best known. Hence statement 1 is correct.

Because of their great reactivity, the free halogen elements are not found in nature. In combined form, fluorine is the most abundant of the halogens in Earth’s crust. The percentages of the halogens in the igneous rocks of Earth’s crust are 0.06 fluorine, 0.031 chlorine, 0.00016 bromine, and 0.00003 iodine. Astatine and tennessine do not occur in nature, because they consist of only short-lived radioactive isotopes. Hence statement 2 is correct.

QUESTION: 11

With reference to the 'National Aquifer Mapping and Management Programme’ (NAQUIM), consider the following statements:

1. It aims to prepare a map of all surface and groundwater sources of water in India.

2. It is being implemented by the Central Water Commission.

Which of the statements given above is/are correct?

Solution: Both statements 1 and 2 are not correct: Central Ground Water Board (CGWB) is implementing the ‘National Aquifer Mapping and Management Programme’ (NAQUIM) for aquifer mapping in the country including in areas that have recorded a high depletion of groundwater, in phases. phases. An aquifer is a body of saturated rock through which water can easily move.

The National Aquifer Mapping and Management Programme (NAQUIM) was initiated as a part of the Ground Water Management and Regulation scheme to delineate and characterize the aquifers to develop plans for groundwater management.

Central Ground Water Board (CGWB) has been entrusted with the responsibilities of developing & disseminating technologies, monitoring national policies for the scientific and sustainable development and management of India’s groundwater resources. CGWB periodically takes up various studies which include groundwater management studies, exploratory drilling programmes, monitoring groundwater level and water quality through a network of groundwater observation wells etc. and the result collected is shared with the concerned States for taking up suitable ground water-specific interventions.

Aquifer maps and management plans are being regularly shared with State Governments through the State Ground Water Coordination Committees, chaired by the concerned Principal Secretaries of the respective States.

QUESTION: 12

Which of the following vitamins are soluble in fat?

1. Vitamin A

2. Vitamin B

3. Vitamin C

4. Vitamin E

5. Vitamin K

Select the correct answer using the code given below.

Solution: Vitamins are classified as either fat-soluble (vitamins A, D, E and K) or water-soluble (vitamins B and C). This difference between the two groups is very important. It determines how each vitamin acts within the body.

The fat-soluble vitamins are soluble in lipids (fats). These vitamins are usually absorbed in fat globules (called chylomicrons) that travel through the lymphatic system of the small intestines and into the general blood circulation within the body. These fat-soluble vitamins, especially vitamins A and E, are then stored in body tissues.

Water-soluble vitamins dissolve in water, which means these vitamins and nutrients dissolve quickly in the body. Unlike fat-soluble vitamins, water-soluble vitamins are carried to the body’s tissues, but the body cannot store them. Any excess amounts of water-soluble vitamins simply pass through the body.

QUESTION: 13

Consider the following statements with reference to Prokaryotic and eukaryotic cells:

1. In Prokaryotic cells, there is a well- defined nucleus and membrane-bound organelles.

2. In Eukaryotic cells, there is no well- defined nucleus and organelles are absent.

Which of the statements given above is/are correct?

Solution: The prokaryotic cells are represented by bacteria, blue-green algae, mycoplasma and PPLO (Pleuro Pneumonia Like Organisms). They are generally smaller and multiply more rapidly than the eukaryotic cells.

Prokaryotes have a cell wall surrounding the cell membrane except in mycoplasma. The fluid matrix filling the cell is the cytoplasm. There is no well-defined nucleus. The genetic material is basically naked, not enveloped by a nuclear membrane. In addition to the genomic DNA (single chromosome/circular DNA), many bacteria have small circular DNA outside the genomic DNA. This smaller DNA is called plasmids. No organelles, like the ones in eukaryotes, are found in prokaryotic cells except for ribosomes. Hence statement 1 is not correct.

The eukaryotes include all the protists, plants, animals and fungi. In eukaryotic cells, there is an extensive compartmentalisation of cytoplasm through the presence of membrane-bound organelles. Eukaryotic cells possess an organised nucleus with a nuclear envelope. Hence statement 2 is not correct. In addition, eukaryotic cells have a variety of complex locomotory and cytoskeletal structures. Their genetic material is organised into chromosomes. All eukaryotic cells are not identical. Plant and animal cells are different as the former possess cell walls, plastids and a large central vacuole which are absent in animal cells. On the other hand, animal cells have centrioles which are absent in almost all plant cells.

QUESTION: 14

Which among the following is known as the powerhouse of the cell and has its own DNA and ribosomes?

Solution: Mitochondria are known as the powerhouses of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules. ATP is known as the energy currency of the cell. The body uses energy stored in ATP for making new chemical compounds and for mechanical work.

Mitochondria have two membrane coverings instead of just one. The outer membrane is very porous while the inner membrane is deeply folded.

These folds create a large surface area for ATP-generating chemical reactions.

Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their own proteins.

QUESTION: 15

Recently a device called 'core catcher' was installed in the Kudankulam nuclear plant. In this context, consider the following statements:

1. A core catcher is a device that supplements the work of the moderators by further slowing down the speed of neutrons in a nuclear reactor.

2. It is made up of materials different from that of the moderator.

Which of the statements given above is/are correct?

Solution: Meltdown accidents that occurred at Chernobyl in Russia in 1986 and at Fukushima in Japan in 2011 sent a wave of shocks across the world. The core catcher device is installed at the bottom of the nuclear station’s protective shell and is designed to save the latter as well as exude radioactive emission in the environment in case of a serious accident.

Core Catchers area cone-shaped metal structure that can prevent such accidents. The structure is double walled, with the gap between the two walls filled with FAOG (ferric and aluminum oxide granules). The core catcher is filled with a ceramic mixture also including ferric oxide and aluminum oxide, called ‘sacrificial material’. The sacrificial material prevents the corium from trickling through and also acts as a cooling mechanism.

The moderator of a nuclear reactor is a substance that slows neutrons down. In traditional nuclear reactors, the moderator is the same thing as the coolant: it's water! When fast neutrons strike the hydrogen atoms in H2O, they slow down a lot (like a billiard ball striking another).

At Kudankulam, it has been installed in the design position under the reactor pit of Unit 3 and has been adapted to the relevant site conditions and safety requirements.

The device has improved seismic resistance, hydro-dynamic, and shock strength as well as equipped with flood protection and simplified installation and assembly technology. Russia completed core supplies for Kudankulam unit 3, consisting of the molten core catcher, the embedded parts of the reactor pit, dry protection, heat-insulation of the cylindrical shell/barrel, truss buckstay and reactor vessel. These are part of the enhanced safety features of the VVER-1000 reactors being installed. Russia is building the Kudankulam Nuclear plant under an intergovernmental agreement

Hence statement 1 is not correct and statement 2 is correct.

QUESTION: 16

Consider the following statements with regard to radiation:

1. Transfer of heat by radiation requires a medium.

2. All hot bodies radiate infrared radiation.

Which of the statements given above is/are correct?

Solution: Statement 1 is not correct: The transfer of heat by radiation does not require any medium. It can take place whether a medium is present or not. When we come out in the sun, we feel warm. How does the heat from the sun reach us? It cannot reach us by conduction or convection as there is no medium such as air in most parts of the space between the earth and the sun. From the sun the heat comes to us by another process known as radiation.

Statement 2 is correct: Since the primary source of infrared radiation is heat or thermal radiation, any object which has a temperature radiates in the infrared. Even objects that we think of as being very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to radiate visible light, it will emit most of its energy in the infrared. For example, hot charcoal may not give off light but it does emit infrared radiation which we feel as heat. The warmer the object, the more infrared radiation it emits.

QUESTION: 17

With reference to human blood, Rh factor is a/an

Solution: Rh factor is an antigen found on the surface of red blood cells. Red blood cells with the antigen are said to be Rh-positive (Rh+). Those without the surface antigen are said to be Rh-negative (Rh-). Blood used in transfusions match donors for Rh status as well as for blood group, as Rh- patients will develop anemia if given Rh+ blood.

QUESTION: 18

Which among the following are exocrine glands in the human body?

1. Mammary glands

2. Pituitary glands

3. Tear ducts

Select the correct answer using the code given below.

Solution: Exocrine glands are cellular sub-structures, organs, in a body that provide a system to secrete substances out and are external to the body.

Exocrine glands secrete their substances through a ductal system. Examples of Exocrine Glands (and Secreted Product)

Lacrimal gland (Tear ducts and glands near each eye) Mammary gland (Breast milk), Eccrine sweat glands (Perspiration or salty water release) Salivary glands (Saliva consisting of fluid with digestive enzymes)

Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones, directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus, and adrenal glands.

Hence only options 1 and 3 are correct.

QUESTION: 19

Which of the following rays or radiations are used in thermal imaging?

Solution: (i) All objects emit infrared energy (heat).

(ii) In general, the hotter an object is, the more radiation it emits.

(iii) A thermal imager (also known as a thermal camera) is essentially a heat sensor that is capable of detecting tiny differences in temperature.

(iv) The device collects the infrared radiation from objects in the scene and creates an electronic image based on information about the temperature differences.

(v) Because objects are rarely precisely the same temperature as other objects around them, a thermal camera can detect them and they will appear as distinct in a thermal image.

(vi) Thermal images are normally grayscale in nature: black objects are cold, white objects are hot and the depth of gray indicates variations between the two.

(vii) Some thermal cameras, however, add color to images to help users identify objects at different temperatures.

(viii)They can be used to search for victims outdoors on a cool night, spot smoldering fires inside a wall, or detect overheating electrical wiring

QUESTION: 20

With reference to Hemoglobin, consider the following statements:

1. It imparts red color to blood.

2. It carries oxygen in the blood.

3. It transports carbon dioxide from tissues to lungs.

Which of the above functions is/are performed by Hemoglobin?

(d)1, 2 and 3

Solution:

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates (with the exception of the fish family Channichthyidae) as well as the tissues of some invertebrates.

Carbon dioxide is transported in the blood from the tissue to the lungs in three ways: o dissolved in the blood or buffered with water as a carbonic acid or bound to proteins, particularly hemoglobin.

Each hemoglobin protein is made up of subunits called hemes, which are what gives blood its red color. More specifically, the hemes can bind iron molecules, and these iron molecules bind oxygen. The blood cells are red because of the interaction between iron and oxygen. Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the rest of the body (i.e. the tissues). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism.

Hence all the options are correct.

 

QUESTION: 21

Consider the following statements with regard to the National Genomic Grid:

1. It is a pan India program to study genes of all patients suffering from all types of genetic diseases.

2. The study will utilize the technique of genome sequencing.

Which of the statements given above is/are correct?

Solution: Recently, the government has announced to set up a National Genomic Grid (NGG), which will study genomic data of cancer patients from India. Hence statement 1 is not correct.

The grid to be formed will be in line with the National Cancer Tissue Biobank (NCTB) set up at the Indian Institute of Technology, Madras and will collect samples from cancer patients, through a network of pan-India collection centers.

The grid will have four parts, with the country divided into east, west, north, and south

The aim is to study genomic factors influencing cancer and identifying the right treatment modalities for the Indian population.

The genomic samples will help researchers to have India-specific studies on cancers. • This study is carried out through the technique of Genome Sequencing that is the process of determining the complete DNA sequence of an organism's genome at a single time. Hence statement 2 is correct.

QUESTION: 22

Which among the following is/are genetic diseases?

1. Haemophilia

2. Down's syndrome

3. Sickle-cell anemia

Select the correct answer using the code given below.

Solution: All of the given diseases are genetic diseases.

Hemophilia: In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood, is affected. Due to this, in an affected individual, a simple cut will result in non-stop bleeding. The heterozygous female (carrier) for hemophilia may transmit the disease to sons. The possibility of a female becoming hemophilic is extremely rare because the mother of such a female has to be at least carrier and the father should be hemophilic.

Sickle-cell anemia: This is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are a carrier for the gene (or heterozygous). It results in an abnormality in the oxygen-carrying protein hemoglobin (hemoglobin S) found in red blood cells. This leads to a rigid, sickle-like shape under certain circumstances.

Down's Syndrome: The cause of this genetic disorder is the presence of an additional copy of chromosome number 21 (trisomy of 21). The affected individual is short-statured with a small round head, furrowed tongue, and partially open mouth. Palm is broad with characteristic palm crease.

Other examples of genetic disorders are: Klinefelter’s Syndrome, Turner’s syndrome, Cystic fibrosis, Colour blindness, Phenylketonuria, Thalassemia.

QUESTION: 23

With reference to the role of antioxidants in the human body, which of the following statements is/are correct?

1. They prevent damage caused by oxidation of fatty acids and proteins by free radicals.

2. They provide protection from asthma, diabetes, and cancer.

Select the correct answer using the codes given below.

Solution: Antioxidants are a group of substances that prevent the damage caused by the oxidation of fatty acids and proteins by oxygen free radicals. ▪

Free radicals are molecules produced when your body breaks down food, or by environmental exposures like tobacco smoke and radiation. Free radicals can damage cells and may play a role in heart disease, cancer, and other diseases.

Antioxidants play important functions in the body. Antioxidants restrict the damage that reactive oxygen free radicals can cause to the cell and cellular components.

They are of primary biological value in giving protection from certain diseases. Some of the diseases that have their origin in deleterious free radical reactions are atherosclerosis, cancer, inflammatory joint diseases, asthma, diabetes, etc.

Hence both the statements are correct.

QUESTION: 24

With reference to phenomena of formation of the rainbow, consider the following statements:

1. A rainbow is always formed in a direction opposite to that of the Sun.

2. The sunlight undergoes refraction and dispersion in the water droplets to form the colors of a rainbow.

Which of the statements given above is/are correct?

Solution: Statement 1 is correct: A rainbow is a natural spectrum appearing in the sky after a rain shower. It is caused by the dispersion of sunlight by tiny water droplets, present in the atmosphere. A rainbow is always formed in a direction opposite to that of the Sun.

Statement 2 is correct: The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colors reach the observer's eye.

Since it involves the total internal reflection of sunlight, the light is reflected back in the direction it originally came from. Hence you can only see a rainbow if your back is facing the sun.

QUESTION: 25

Consider the following statements regarding Thorium:

1. It is largely imported in India to meet nuclear energy demands.

2. Its deposits in India mainly occur in the Vindhyan system of rocks .|S_E_P]

3. It can be directly used as fuel in a nuclear reactor.

Which of the statements given above is/are correct?

Solution: Statement 1 is not correct: The country's thorium reserves make up 25 percent of the global reserves. It can easily be used as a fuel to cut down on the import of Uranium from different countries. The Atomic Minerals Directorate for Exploration and Research (AMD), a constituent unit of Department of Atomic Energy (DAE), has so far established 11.93 million tonnes of in situ resources Monazite (Thorium bearing mineral) in the country, which contains about 1.07 million tonnes of thorium.

Statement 2 is not correct: Monazite (thorium bearing mineral) sands are found in Kerala, Andhra Pradesh, Tamil Nadu, etc. whereas, the Vindhyan System of rocks stand over the Cuddapah rocks and cover large areas in Madhya Pradesh, Chhattisgarh, Uttar Pradesh, and Rajasthan. This system contains rocks like limestones, sandstones, shales, and slates which are useful as building materials.

State

Monazite (Million tonnes)

Odisha

2.41

Andhra Pradesh

3.72

Tamil Nadu

2.46

Kerala

1.90

West Bengal

1.22

Jharkhand

0.22

Total

11.93